Compound and an Organic Semiconducting Layer, an Organic Electronic Device and a Display or Lighting Device Comprising the Same

ABSTRACT

The present invention relates to a compound of formula (I); an organic semiconducting layer, an organic electronic device, a display device or a lighting device comprising the same.

The present invention relates to a compound as well as to an organic semiconducting layer comprising the same. The invention further relates to an organic electronic device comprising the organic semiconducting layer, respectively the compound.

Furthermore, the invention is related to a display device or alighting device comprising the organic electronic device.

BACKGROUND ART

Organic light-emitting diodes (OLEDs), which are self-emitting devices, have a wide viewing angle, excellent contrast, quick response, high brightness, excellent driving voltage characteristics, and color reproduction. A typical OLED includes an anode, a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ET), and a cathode, which are sequentially stacked on a substrate. In this regard, the HTL, the EML, and the ETL are thin films formed from organic and/or organometallic compounds.

When a voltage is applied to the anode and the cathode, holes injected from the anode electrode move to the EML, via the HTL, and electrons injected from the cathode electrode move to the EML, via the ETL, The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted. The injection and flow of holes and electrons should be balanced, so that an OLED having the above-described structure has excellent efficiency.

However, there is still a need to improve the electronic properties of respective compounds for use in organic electronic devices, in particular for improving the performance thereof, and to provide respective organic electronic devices having improved performance. It is an particular aim of the present invention to improve the performance of top emission OLEDs, in particular with respect to operating voltage and efficiency thereof.

It is, therefore, an object of the present invention to provide novel organic electronic devices and compounds for use therein overcoming drawbacks of the prior art, in particular to provide novel compounds having improved properties and being suitable to improve the operating voltage and efficiency of organic electronic devices comprising the same, in particular when being used in an electron transport layer thereof.

This object is achieved by a compound of formula I

wherein R¹ and R² are independently selected from the group consisting of substituted or unsubstituted C₆ to C₄₈ aryl and substituted or unsubstituted C₂ to C₄₂ heteroaryl; the substituents of R¹ and R², if present, are selected from the group consisting of deuterium, fluorine, RF, C₁ to C₂₀ linear alkyl, C₃ to C₂₀ branched alkyl, C₁ to C₁₂ linear fluorinated alkyl, CN, RCN, C₆ to C₂₀ aryl, C₂ to C₂₀ heteroaryl, P(═O)R′R″, wherein each R, R′ and R″ is independently selected from the group consisting of C₁ to C₂₀ linear alkyl, C₁ to C₂₀ alkoxy, C₁ to C₂₀ thioalkyl, C₃ to C₂₀ branched alkyl, C₃ to C₂₀ cyclic alkyl, C₃ to C₂₀ branched alkoxy, C₃ to C₂₀ cyclic alkoxy, C₃ to C₂₀ branched thioalkyl, C₁ to C₂₀ cyclic thioalkyl, C₆ to C₂ aryl and C₂ to C₂₀ heteroaryl; n and m are independently selected from 0, 1, 2 and n+m≥1, alternatively n+m is from 1 to 3; wherein at least one of R¹ and R² is connected to the ring Y, respectively the ring Z, by a spacer unit, wherein the spacer unit is independently selected from substituted or unsubstituted C₆ to C₁₈ arylene or substituted or unsubstituted C₂ to C₂₀ heteroarylene; wherein in case that the spacer unit is substituted the one or more substituent(s) are independently selected from the group consisting of deuterium, C₂ to C₁₄ aryl, C₂ to C₂₀ heteroaryl, CN-substituted C₆ to C₁₄ aryl, CN, P(═O)R′R″, wherein R and R″ may be the same or different and are independently selected from C₁ to C₁₀ alkyl or C₆ to C₁₂ aryl; provided that if the spacer unit is phenylene or phenyl-substituted phenylene the group R¹, respectively R², connected via this spacer unit to the ring Y, respectively Z, is not phenyl; provided that if the spacer unit is C₂ to C₂₀ heteroaryl, then at least one of a substituent on the spacer unit and the group R¹, respectively R², connected to the spacer unit is a heteroaryl.

It was surprisingly found by the inventors that the inventive compounds are suitable to improve the performance of an organic electronic device comprising the same, in particular the performance of top emission OLEDs comprising the same in an electron transport layer thereof. In particular, it was observed that the performance of such devices can be improved with respect to operating voltage and efficiency when using the inventive compounds.

In the Formula (I) above, it should be understood that “Y” and “Z” have no “chemical meaning”, i.e. are not generic expressions directed to a specific chemical moiety.

Rather, the letters “Y” and “Z” are merely used for denoting the very left ring and the very right ring benzo[4,5]imidazo[1,2-A]quinolinylene moiety comprised in Formula (I) to explain the binding position between the respective rings and groups R¹ and R².

In accordance with Formula (I), the group R¹ may be connected to the benzo[4,5]imidazo[1,2-A]quinolinylene moiety in one of the positions labelled with the asterisk symbol “*” in the following formula.

Likewise, the group R² may be connected to the benzo[4,5]imidazo[1,2-A]quinolinylene moiety in any position labelled with the asterisk symbol “*” in the following formula

In case that the compound of Formula (I) comprises more than one R¹ and/or more than one R² each of these groups may be bound to respective different positions labelled with “*”.

According to Formula (I), it is required that at least one of R and R² is connected to the ring Y, respectively the ring Z, by a spacer unit. That is, in case that the compound of Formula (I) does only comprise one of the groups selected from R¹ and R² (that is n+m=1), this group is mandatorily connected to the respective ring via the spacer unit. In case that the compound of Formula (I) comprises more than one group selected from R¹ and R² (that is in case that n+m>1), it is required that at least one of these groups R¹/R² is connected to the benzo[4,5]imidazo[1,2-A]quinolinylene moiety via the spacer unit. Likewise, it is possible that two or more of these groups are connected this way.

The connection via the spacer unit is achieved in that a first bond is formed between the spacer unit and the benzo[4,5]imidazo[1,2-A]quinolinylene moiety at one of the above positions labelled with the “*”. A further bond is formed between the spacer unit and the respective group R¹/R². That is, the spacer unit is a divalent group forming one bond to the group R¹/R² and another bond to the benzo[4,5]imidazo[1,2-A]quinolinylene moiety.

According to Formula (I), such compounds in which the spacer unit is phenylene or phenyl-substituted phenylene and, at the same time, only one of either R¹ or R² is present and the respective R¹ and R² is phenyl are excluded. That is, compounds in which the spacer unit and the respective group R¹/R² form together a biphenyl or a triphenyl moiety are excluded. Exemplary compounds excluded this way are the following structures.

Likewise, it is provided that in case that the spacer unit is C₂ to C₂₀ heteroaryl, then at least one of a substituent on the spacer unit or the group R¹, respectively R², connected to the spacer unit is heteroaryl. In other words, in such cases where a heteroaryl spacer unit is used to connect an aryl group to the benzo[4,5]imidazo[1,2-A]quinolinylene moiety are excluded. An exemplary structure excluded this way is the following

It has been found by the inventors that certain embodiments described below are advantageous to further improve the performance of organic electronic devices comprising such compounds with respect to voltage and efficiency thereof. Best results were achieved when combining two or more of these embodiments.

The total number of aromatic rings in the molecule may be from 6 to 15, alternatively from 6 to 11.

The spacer unit may be selected from C₆ to C₄ aryl, O-containing C₃ to C₁₂ heteroaryl, or N-containing C₃ to C₁₂ heteroaryl.

In particular, the spacer unit may be selected from phenylene, biphenylene, naphthylene, anthracenylene, pyridinylene, diazinylene, dibenzofuranylene and triazinylene, wherein the respective group may be substituted or unsubstituted.

The spacer unit may be selected from substituted or unsubstituted C₆ to C₄ arylene, alternatively selected from anthracenylene or phenylene, alternatively is phenylene.

In case that m and/or n is 2, the respective spacer unit may carry one or two of R¹, respectively R².

The groups R¹ and R² may independently be selected from C₆ to C₁₄ aryl, O-containing C₃ to C₁₇ heteroaryl or N-containing C₃ to C₁₇ heteroaryl.

In particular, R¹ and R² may independently be selected from the group consisting of phenyl, biphenyl, naphthyl, anthracenyl, dibenzofuranyl, pyridyl, diazinyl, triazinyl, phenanthrolinyl, carbazolyl, benzoacridinyl, quinazolinyl, and fluoranthenyl, wherein the respective group may be substituted or unsubstituted.

The one or more substituent(s) if present on the spacer unit and/or the group R¹ and/or the group R² may independently be selected from C₆ to C₄ aryl, O-containing C₄ to C₁₂ heteroaryl, N-containing C₄ to C₂ heteroaryl, cyanophenyl, CN or P(═O)R² with R being methyl or phenyl.

In particular, the one or more substituent(s) if present on the spacer unit and/or the group R¹ and/or the group R² may independently be selected from the group consisting of phenyl, biphenyl, naphthyl, dibenzofuranyl, cyanophenyl, diphenylphosphinoxide, dimethylphosphinoxide, CN, 9,9-dimethylfluorenyl, carbazolyl and pyridinyl.

In certain embodiments, it may be provided that two or more of the above embodiments are combined.

The compound of formula (I) may be represented by one of the following formulas 1 to 37

It may be provided that the two compounds represented by the following formulae are excluded.

The object is further achieved by an organic semiconducting layer comprising the compound of formula (I) as defined herein.

It may be provided that the organic semiconducting layer does not contain a dopant or an additive.

Alternatively, the organic semiconducting layer may comprise an n-type additive which is selected from a metal, a metal salt or a metal complex.

The n-type additive may be an n-type dopant. The n-type dopant may be a reductive dopant in the sense that it donates an electron to the first or second matrix compound.

In this regard, the metal may be selected from alkali metal, alkaline earth metal and rare earth metal. The metal salt may be the salt of an alkali metal, the salt of an alkaline earth metal or the salt of a rare earth metal. The metal complex may be an organic alkali metal complex, alternatively an alkali metal complex, alternatively LiQ or alkali borate.

The organic semiconducting layer may further comprise at least one second matrix compound. This second compound matrix is not an n-type dopant or an n-type additive.

The organic semiconducting layer may be essentially non-emissive.

The object is further achieved by an organic electronic device comprising the inventive semiconducting layer.

It may be provided that the organic electronic device comprises two emission layers and that the organic semiconducting layer is arranged between the two emission layers. In case that the organic electronic device comprises more than two emission layers, the organic semiconducting layer is arranged between (at least) two of them.

The organic electronic device may further comprise an auxiliary electron transport layer and the organic semiconducting layer may be arranged in direct contact with the auxiliary electron transport layer. The compound of formula (I) may be comprised in the auxiliary electron transport layer or, alternatively, the auxiliary electron transport layer may consist of the compound of formula (I).

The organic electronic device may comprise an emission layer and the semiconducting layer may be arranged in direct contact with the emission layer.

The organic electronic device may comprise an electron transport layer and the organic semiconducting layer may be arranged in direct contact with the electron transport layer.

The organic electronic device may comprise a cathode and the organic semiconducting layer may be arranged in direct contact with the cathode.

The object is further achieved by a display device comprising the inventive organic electronic device.

Finally, the object is achieved by a lighting device comprising the inventive organic electronic device.

Embodiments and combinations thereof referred to above with respect to the inventive compound are also embodiments for realizing the organic semiconducting layer, the organic electronic device, the display device or the lighting device as disclosed herein.

Further Layers

In accordance with the invention, the organic electronic device may comprise, besides the layers already mentioned above, further layers. Exemplary embodiments of respective layers are described in the following:

Substrate

The substrate may be any substrate that is commonly used in manufacturing of, electronic devices, such as organic light-emitting diodes. If light is to be emitted through the substrate, the substrate shall be a transparent or semitransparent material, for example a glass substrate or a transparent plastic substrate. If light is to be emitted through the top surface, the substrate may be both a transparent as well as a non-transparent material, for example a glass substrate, a plastic substrate, a metal substrate or a silicon substrate.

Anode Electrode

Either a first electrode or a second electrode comprised in the inventive organic electronic device may be an anode electrode. The anode electrode may be formed by depositing or sputtering a material that is used to form the anode electrode. The material used to form the anode electrode may be a high work-function material, so as to facilitate hole injection. The anode material may also be selected from a low work function material (i.e. aluminum). The anode electrode may be a transparent or reflective electrode. Transparent conductive oxides, such as indium tin oxide (ITO), indium zinc oxide (IZO), tin-dioxide (SnO₂), aluminum zinc oxide (AlZO) and zinc oxide (ZnO), may be used to form the anode electrode. The anode electrode may also be formed using metals, typically silver (Ag), gold (An), or metal alloys.

Hole Injection Layer

A hole injection layer (HIL) may be formed on the anode electrode by vacuum deposition, spin coating, printing, casting, slot-die coating, Langmuir-Blodgett (LB) deposition, or the like. When the HIL is formed using vacuum deposition, the deposition conditions may vary according to the compound that is used to form the HIL, and the desired structure and thermal properties of the HIL. In general, however, conditions for vacuum deposition may include a deposition temperature of 100° C. to 500° C., a pressure of 10-8 to 10-3 Torr (1 Torr equals 133.322 Pa), and a deposition rate of 0.1 to 10 n/sec.

When the HIL is formed using spin coating or printing, coating conditions may vary according to the compound that is used to form the IL, and the desired structure and thermal properties of the HIL. For example, the coating conditions may include a coating speed of about 2000 rpm to about 5000 rpm, and a thermal treatment temperature of about 80° C. to about 200° C. Thermal treatment removes a solvent after the coating is performed.

The IL may be formed of any compound that is commonly used to form a HIL. Examples of compounds that may be used to form the HIL include a phthalocyanine compound, such as copper phthalocyanine (CuPc), 4,4′,4″-tris (3-methylphenylphenylamino) triphenylamine (m-MTDATA), TDATA, 2T-NATA, polyaniline/dodecylbenzenesulfonic acid (Pani/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (Pani/CSA), and polyaniline)/poly(4-styrenesulfonate (PANI/PSS).

The HIL may comprise or consist of p-type dopant and the p-type dopant may be selected from tetrafluoro-tetracyanoquinonedimethane (F4TCNQ), 2,2′-(perfluoronaphthalen-2,6-diylidene) dimalononitrile or 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) but not limited hereto. The HIL may be selected from a hole-transporting matrix compound doped with a p-type dopant. Typical examples of known doped hole transport materials are: copper phthalocyanine (CuPe), which HOMO level is approximately −5.2 eV, doped with tetrafluoro-tetracyanoquinonedimethane (F4TCNQ), which LUMO level is about −5.2 eV; zinc phthalocyanine (ZnPc) (HOMO=−5.2 eV) doped with F4TCNQ; α-NPD (N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine) doped with F4TCNQ. α-NPD doped with 2,2′-(perfluoronaphthalen-2,6-diylidene) dimalononitrile. The p-type dopant concentrations can be selected from 1 to 20 wt.-%, more preferably from 3 wt.-% to 10 wt.-%.

The thickness of the HIL may be in the range from about 1 nm to about 100 nm, and for example, from about 1 nm to about 25 nm. When the thickness of the IL is within this range, the IL may have excellent hole injecting characteristics, without a substantial penalty in driving voltage.

Hole Transport Layer

A hole transport layer (HTL) may be formed on the HIL by vacuum deposition, spin coating, slot-die coating, printing, casting, Langmuir-Blodgett (LB) deposition, or the like. When the HTL is formed by vacuum deposition or spin coating, the conditions for deposition and coating may be similar to those for the formation of the HIL. However, the conditions for the vacuum or solution deposition may vary, according to the compound that is used to form the HTL.

The HTL may be formed of any compound that is commonly used to form a HTL. Compounds that can be suitably used are disclosed for example in Yasuhiko Shirota and Hiroshi Kageyama, Chem. Rev. 2007, 107, 953-1010 and incorporated by reference. Examples of the compound that may be used to form the HTL are: carbazole derivatives, such as N-phenylcarbazole or polyvinylcarbazole; benzidine derivatives, such as N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), or N,N′-di(naphthalen-1-yl)-N,N′-diphenyl benzidine (alpha-NPD); and triphenylamine-based compound, such as 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA). Among these compounds, TCTA can transport holes and inhibit excitons from being diffused into the EML.

The thickness of the HTL may be in the range of about 5 nm to about 250 nm, preferably, about 10 nm to about 200 nm, further about 20 nm to about 190 nm, further about 40 nm to about 180 nm, further about 60 nm to about 170 nm, further about 80 nm to about 160 nm, further about 100 nm to about 160 nm, further about 120 nm to about 140 nm. A preferred thickness of the HTL may be 170 nm to 200 nm.

When the thickness of the HTL is within this range, the HTL may have excellent hole transporting characteristics, without a substantial penalty in driving voltage.

Electron Blocking Layer

The function of an electron blocking layer (EBL) is to prevent electrons from being transferred from an emission layer to the hole transport layer and thereby confine electrons to the emission layer. Thereby, efficiency, operating voltage and/or lifetime are improved. Typically, the electron blocking layer comprises a triarylamine compound. The triarylamine compound may have a LUMO level closer to vacuum level than the LUMO level of the hole transport layer. The electron blocking layer may have a HOMO level that is further away from vacuum level compared to the HOMO level of the hole transport layer. The thickness of the electron blocking layer may be selected between 2 and 20 nm.

If the electron blocking layer has a high triplet level, it may also be described as triplet control layer.

The function of the triplet control layer is to reduce quenching of triplets if a phosphorescent green or blue emission layer is used. Thereby, higher efficiency of light emission from a phosphorescent emission layer can be achieved. The triplet control layer is selected from triarylamine compounds with a triplet level above the triplet level of the phosphorescent emitter in the adjacent emission layer. Suitable compounds for the triplet control layer, in particular the triarylamine compounds, are described in EP 2 722 908 A1.

Emission Layer (EML)

The EML may be formed on the HTL by vacuum deposition, spin coating, slot-die coating, printing, casting, LB deposition, or the like. When the EML is formed using vacuum deposition or spin coating, the conditions for deposition and coating may be similar to those for the formation of the HIL. However, the conditions for deposition and coating may vary, according to the compound that is used to form the EML.

It may be provided that the emission layer does not comprise the compound of Formula (I).

The emission layer (EML) may be formed of a combination of a host and an emitter dopant. Example of the host are Alq3, 4,4′-N,N′-dicarbazole-biphenyl (CBP), poly(n-vinylcarbazole) (PVK), 9,10-di(naphthalene-2-yl)anthracene (ADN), 4,4′,4″-tris(carbazol-9-yl)-triphenylamine (TCTA), 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI), 3-tert-buty-9,1-di-2-naphthylanthracene (TBADN), distyrylarylene (DSA) and bis((2-hydroxyphenyl)benzo-thiazolate)zinc (Zn(BTZ)2).

The emitter dopant may be a phosphorescent or fluorescent emitter. Phosphorescent emitters and emitters which emit light via a thermally activated delayed fluorescence (TADF) mechanism may be preferred due to their higher efficiency. The emitter may be a small molecule or a polymer.

Examples of red emitter dopants are PtOEP, Ir(piq)3, and Btp2lr(acac), but are not limited thereto. These compounds are phosphorescent emitters, however, fluorescent red emitter dopants could also be used.

Examples of phosphorescent green emitter dopants are Ir(ppy)3 (ppy=phenylpyridine), Ir(ppy)2(acac), Ir(mpyp)3.

Examples of phosphorescent blue emitter dopants are F2Irpic, (F2ppy)2Ir(tmd) and Ir(dfppz)3 and ter-fluorene. 4,4′-bis(4-diphenyl aminostyryl)biphenyl (DPAVBi), 2,5,8,1-tetra-tert-butyl perylene (TBPe) are examples of fluorescent blue emitter dopants.

The amount of the emitter dopant may be in the range from about 0.01 to about 50 parts by weight, based on 100 parts by weight of the host. Alternatively, the emission layer may consist of a light-emitting polymer. The EML may have a thickness of about 10 nm to about 100 nm, for example, from about 20 nm to about 60 nm. When the thickness of the EML is within this range, the EML may have excellent light emission, without a substantial penalty in driving voltage.

Hole Blocking Layer (HBL)

A hole blocking layer (HBL) may be formed on the EML, by using vacuum deposition, spin coating, slot-die coating, printing, casting, LB deposition, or the like, in order to prevent the diffusion of holes into the ETL. When the EML comprises a phosphorescent dopant, the HBL may have also a triplet exciton blocking function. The hole blocking layer may be the inventive organic semiconducting layer comprising or consisting of the inventive compound represented by the general Formula (I) as defined above.

The HBL may also be named auxiliary electron transport layer or a-ETL and electron transport layer 1 or ETL-1.

The HBL of the organic electronic device may comprise the compound represented by general Formula (I). Alternatively, the HBL may consist of the compound of formula (I).

When the HBL is formed using vacuum deposition or spin coating, the conditions for deposition and coating may be similar to those for the formation of the HIL. However, the conditions for deposition and coating may vary, according to the compound that is used to form the HBL. Any compound that is commonly used to form a HBL may be used. Examples of compounds for forming the HBL include oxadiazole derivatives, triazole derivatives, and phenanthroline derivatives.

The HBL may have a thickness in the range from about nm to about 100 nm, for example, from about 10 nm to about 30 nm. When the thickness of the HBL is within this range, the HBL may have excellent hole-blocking properties, without a substantial penalty in driving voltage.

Electron Transport Layer (ETL)

The OLED according to the present invention may comprise an electron transport layer (ETL). In accordance with one preferred embodiment of the invention, the electron transport layer may be the inventive organic semiconducting layer comprising the inventive compound represented by the general Formula (I) as defined herein.

In an embodiment the ETL may consist of a compound of Formula (I).

According to various embodiments the OLED may comprise an electron transport layer or an electron transport layer stack comprising at least a first electron transport layer and at least a second electron transport layer.

By suitably adjusting energy levels of particular layers of the ETL, the injection and transport of the electrons may be controlled, and the holes may be efficiently blocked. Thus, the OLED may have long lifetime.

The electron transport layer of the organic electronic device may comprise the compound represented by general Formula (I) as defined above as the organic electron transport matrix (ETM) material which can also be referred to as a matrix compound. The electron transport layer may comprise, besides or instead of the compound represented by the general Formula (I), further ETM materials know in the art. In one embodiment the electron transport layer comprises besides of the compound represented by the general Formula (I), one further ETM material which is referred to as a second matrix compound. Likewise, the electron transport layer may comprise as the only electron transport matrix material the compound represented by general Formula (I). In case that the inventive organic electronic device comprises more than one electron transport layers, the compound represented by the general Formula (I) may be comprised in only one of the electron transport layers, in more than one of the electron transport layers or in all of the electron transport layers. In accordance with the invention, the electron transport layer may comprise, besides the ETM material, at least one additive as defined below.

Further, the organic semiconducting layer may comprise one or more n-type additives. The additive may be an n-type dopant. The additive can be alkali metal, alkali metal compound, alkaline earth metal, alkaline earth metal compound, transition metal, transition metal compound or a rare earth metal. In another embodiment, the metal can be one selected from a group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, and Yb. In another embodiment, the n-type dopant can be one selected from a group consisting of Cs, K, Rb, Mg, Na, Ca, Sr, Eu and Yb. In an embodiment the alkali metal compound may be 8-Hydroxyquinonolato-lithium (LiQ), Lithium tetra(1H-pyrazol-1-yl)borate or Lithium 2-(diphenylphosphoryl)phenolate. Suitable compounds for the ETM (which may be used in addition to the inventive compound represented by the general Formula (I) as defined above) are not particularly limited. In one embodiment, the electron transport matrix compounds consist of covalently bound atoms. Preferably, the electron transport matrix compound comprises a conjugated system of at least 6, more preferably of at least 10 delocalized electrons. In one embodiment, the conjugated system of delocalized electrons may be comprised in aromatic or heteroaromatic structural moieties, as disclosed e.g. in documents EP 1970 371 A1 or WO 2013/079217 A1.

According to another aspect of the present invention organic semiconducting layer may comprise one or more alkali metal salt and alkali metal organic complex

-   -   the alkali metal salt is selected from the group comprising LiF,         LiCl, LiBr or LiI, and preferably LiF;     -   the alkali metal organic complex is selected from the group         comprising a lithium quinolinolate, lithium borate, lithium         phenolate, lithium pyridinolate or comprises a lithium with a         Schiff base ligand;     -   preferably the lithium quinolinolate complex has the formula IV,         V or VI:

wherein

-   -   A₁ to A₆ are same or independently selected from CHI, CR, N, O;     -   R is same or independently selected from hydrogen, halogen,         alkyl or aryl or heteroaryl with 1 to 20 carbon atoms; and more         preferred A1 to A6 are CH;     -   preferably the borate based organic ligand is a         tetra(1H-pyrazol-1-yl)borate;     -   preferably the phenolate is a 2-(pyridin-2-yl)phenolate, a         2-(diphenylphosphoryl)phenolate, an imidazol phenolates, or         2-(pyridin-2-yl)phenolate and more preferred         2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenolate;     -   preferably the pyridinolate is a         2-(diphenylphosphoryl)pyridin-3-olate,     -   preferably the lithium Schiff base has the structure 100, 101,         102 or 103:

According to another aspect of the present invention, the OLED may comprise an electron transport layer or an electron transport layer stack comprising at least a first electron transport layer and at least a second electron transport layer wherein the first first electron transport layer may comprise the compound represented by general Formula (I).

Electron Injection Layer (EIL)

An optional EIL, which may facilitates injection of electrons from the cathode, may be formed on the ETL, preferably directly on the electron transport layer. Examples of materials for forming the EIL include lithium 8-hydroxyquinolinolate (LiQ), LiF, NaCl, CsF, LiAO, BaO, Ca, Ba, Yb, Mg which are known in the art. Deposition and coating conditions for forming the EIL are similar to those for formation of the HIL, although the deposition and coating conditions may vary, according to the material that is used to form the EIL. The EIL may be the organic semiconducting layer comprising the compound of Formula (I).

The thickness of the EIL may be in the range from about 0.1 nm to about 10 nm, for example, in the range from about 0.5 nm to about 9 nm. When the thickness of the EIL is within this range, the EIL may have satisfactory electron-injecting properties, without a substantial penalty in driving voltage.

Cathode Electrode

The cathode electrode is formed on the EIL if present. The cathode electrode may be formed of a metal, an alloy, an electrically conductive compound, or a mixture thereof. The cathode electrode may have a low work function. For example, the cathode electrode may be formed of lithium (Li), magnesium (Mg), aluminum (Al), aluminum (Al)-lithium (Li), calcium (Ca), barium (Ba), ytterbium (Yb), magnesium (Mg)-indium (In), magnesium (Mg)-silver (Ag), or the like. Alternatively, the cathode electrode may be formed of a transparent conductive oxide, such as ITO or IZO.

The thickness of the cathode electrode may be in the range from about 5 nm to about 1000 nm, for example, in the range from about 10 nm to about 100 nm. When the thickness of the cathode electrode is in the range from about 5 nm to about 50 nm, the cathode electrode may be transparent or semitransparent even if formed from a metal or metal alloy.

It is to be understood that the cathode electrode is not part of an electron injection layer or the electron transport layer.

Charge Generation Layer/Hole Generating Layer

The charge generation layer (CGL) may comprise a p-type and an n-type layer. An interlayer may be arranged between the p-type layer and the n-type layer.

Typically, the charge generation layer is a pn junction joining an n-type charge generation layer (electron generating layer) and a hole generating layer. The n-side of the pn junction generates electrons and injects them into the layer which is adjacent in the direction to the anode. Analogously, the p-side of the p-n junction generates holes and injects them into the layer which is adjacent in the direction to the cathode.

Charge generating layers are used in tandem devices, for example, in tandem OLEDs comprising, between two electrodes, two or more emission layers. In a tandem OLED comprising two emission layers, the n-type charge generation layer provides electrons for the first light emission layer arranged near the anode, while the hole generating layer provides holes to the second light emission layer arranged between the first emission layer and the cathode.

Suitable matrix materials for the hole generating layer may be materials conventionally used as hole injection and/or hole transport matrix materials. Also, p-type dopant used for the hole generating layer can employ conventional materials. For example, the p-type dopant can be one selected from a group consisting of tetrafluore-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), derivatives of tetracyanoquinodimethane, radialene derivatives, iodine, FeCl3, FeF3, and SbCl5. Also, the host can be one selected from a group consisting of N,N′-di(naphthalen-1-yl)-N,N-diphenyl-benzidine (NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1-biphenyl-4,4′-diamine (TPD) and N,N′,N′-tetranaphthyl-benzidine (TNB). The p-type charge generation layer may consist of CNHAT.

The n-type charge generating layer may be the layer comprising the compound of Formula (I). The n-type charge generation layer can be layer of a neat n-type dopant, for example of an electropositive metal, or can consist of an organic matrix material doped with the n-type dopant. In one embodiment, the n-type dopant can be alkali metal, alkali metal compound, alkaline earth metal, alkaline earth metal compound, a transition metal, a transition metal compound or a rare earth metal. In another embodiment, the metal can be one selected from a group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Th, Dy, and Yb. More specifically, the n-type dopant can be one selected from a group consisting of Cs, K, Rb, Mg, Na, Ca, Sr, Eu and Yb. Suitable matrix materials for the electron generating layer may be the materials conventionally used as matrix materials for electron injection or electron transport layers. The matrix material can be for example one selected from a group consisting of triazine compounds, hydroxyquinoline derivatives like tris(8-hydroxyquinoline)aluminum, benzazole derivatives, and silole derivatives.

The hole generating layer is arranged in direct contact to the n-type charge generation layer.

Organic Electronic Device

An organic electronic device according to the invention comprises an organic semiconducting layer comprising a compound according to Formula (I).

An organic electronic device according to one embodiment may include a substrate, an anode layer, an organic semiconducting layer comprising a compound of Formula (I) and a cathode layer.

An organic electronic device according to one embodiment comprises at least one organic semiconducting layer comprising at least one compound of Formula (I), at least one anode layer, at least one cathode layer and at least one emission layer, wherein the organic semiconducting layer is preferably arranged between the emission layer and the cathode layer.

An organic light-emitting diode (OLED) according to the invention may include an anode, a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) comprising at least one compound of Formula (I), and a cathode, which are sequentially stacked on a substrate. In this regard, the HTL, the EML, and the ETL are thin films formed from organic compounds.

An organic electronic device according to one embodiment can be a light emitting device, thin film transistor, a battery, a display device or a photovoltaic cell, and preferably a light emitting device.

According to another aspect of the present invention, there is provided a method of manufacturing an organic electronic device, the method using:

-   -   at least one deposition source, preferably two deposition         sources and more preferred at least three deposition sources.

The methods for deposition that can be suitable comprise:

-   -   deposition via vacuum thermal evaporation;     -   deposition via solution processing, preferably the processing is         selected from spin-coating, printing, casting; and/or     -   slot-die coating.

According to various embodiments of the present invention, there is provided a method using:

-   -   a first deposition source to release the compound of Formula (I)         according to the invention, and     -   a second deposition source to release the metal, a metal salt or         an alkali or alkaline earth metal complex; alternatively an         organic alkali or alkaline earth metal complex; alternatively         8-hydroxyquinolinolato lithium or alkali borate;         the method comprising the steps of forming the organic         semiconducting layer; whereby for an organic light-emitting         diode (OLED):     -   the organic semiconducting layer is formed by releasing the         compound of Formula (I) according to the invention from the         first deposition source and a metal, a metal salt or an alkali         or alkaline earth metal complex; alternatively an organic alkali         or alkaline earth metal complex; alternatively         8-hydroxyquinolinolato lithium or alkali borate, from the second         deposition source.

According to various embodiments of the present invention, the method may further include forming on the anode electrode, an emission layer and at least one layer selected from the group consisting of forming a hole injection layer forming a hole transport layer, or forming a hole blocking layer, between the anode electrode and the first electron transport layer.

According to various embodiments of the present invention, the method may further include the steps for forming an organic light-emitting diode (OLED), wherein

-   -   on a substrate a first anode electrode is formed,     -   on the first anode electrode an emission layer is formed,     -   on the emission layer an electron transport layer stack is         formed, optionally a hole blocking layer is formed on the         emission layer and an organic semiconducting layer is formed,     -   and finally a cathode electrode is formed,     -   optional a hole injection layer, a hole transport layer, and a         hole blocking layer, formed in that order between the first         anode electrode and the emission layer,     -   optional an electron injection layer is formed between the         organic semiconducting layer and the cathode electrode.

According to various embodiments of the present invention, the method may further comprise forming an electron injection layer on the organic semiconducting layer. However, according to various embodiments of the OLED of the present invention, the OLED may not comprise an electron injection layer.

According to various embodiments, the OLED may have the following layer structure, wherein the layers having the following order:

anode, hole injection layer, first hole transport layer, second hole transport layer, emission layer, optional hole blocking layer, organic semiconducting layer comprising a compound of Formula (I) according to the invention, optional electron injection layer, and cathode.

According to another aspect of the invention, it is provided an electronic device comprising at least one organic light emitting device according to any embodiment described throughout this application, preferably, the electronic device comprises the organic light emitting diode in one of embodiments described throughout this application. More preferably, the electronic device is a display device.

In one embodiment, the organic electronic device according to the invention comprising an organic semiconducting layer comprising a compound according to Formula (I) may further comprise a layer comprising a radialene compound and/or a quinodimethane compound.

In one embodiment, the radialene compound and/or the quinodimethane compound may be substituted with one or more halogen atoms and/or with one or more electron withdrawing groups. Electron withdrawing groups can be selected from nitrile groups, halogenated alkyl groups, alternatively from perhalogenated alkyl groups, alternatively from perfluorinated alkyl groups. Other examples of electron withdrawing groups may be acyl, sulfonyl groups or phosphoryl groups.

Alternatively, acyl groups, sulfonyl groups and/or phosphoryl groups may comprise halogenated and/or perhalogenated hydrocarbyl. In one embodiment, the perhalogenated hydrocarbyl may be a perfluorinated hydrocarbyl. Examples of a perfluorinated hydrocarbyl can be perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluoroisopropyl, perfluorobutyl, perfluorophenyl, perfluorotolyl; examples of sulfonyl groups comprising a halogenated hydrocarbyl may be trifluoromethylsulfonyl, pentafluoroethylsulfonyl, pentafluorophenylsulfonyl, heptafluoropropylsufonyl, nonafluorobutylsulfonyl, and like.

In one embodiment, the radialene and/or the quinodimethane compound may be comprised in a hole injection, hole transporting and/or a hole generation layer.

In one embodiment, the radialene compound may have Formula (XX) and/or the quinodimethane compound may have Formula (XXIa) or (XXIb):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R¹¹, R¹², R₁₅, R¹⁶, R²⁰, R²¹ are independently selected from above mentioned electron withdrawing groups and R⁹, R¹⁰, R¹³, R¹⁴, R¹⁷, R¹⁸, R¹⁹, R²², R²³ and R²⁴ are independently selected from H, halogen and above mentioned electron withdrawing groups.

Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following examples. Reference will now be made in detail to the exemplary aspects.

Details and Definitions of the Invention

In the present specification, when a definition is not otherwise provided, an “alkyl group” may refer to an aliphatic hydrocarbon group. The alkyl group may refer to “a saturated alkyl group” without any double bond or triple bond. The term “alkyl” as used herein shall encompass linear as well as branched and cyclic alkyl. For example, C₃-alkyl may be selected from n-propyl and iso-propyl. Likewise, C₄-alkyl encompasses n-butyl, see-butyl and t-butyl. Likewise, C₆-alkyl encompasses n-hexy and cyclo-hexyl.

The subscribed number n in C_(n) relates to the total number of carbon atoms in the respective alkyl, arylene, heteroarylene or aryl group.

The term “aryl” or “arylene” as used herein shall encompass aromatic groups like phenyl (C₆-aryl), fused aromatics, such as naphthalene, anthracene, phenanthracene, tetracene etc. Further encompassed are biphenyl and oligo- or polyphenyls, such as terphenyl etc. Further encompassed shall be any further aromatic hydrocarbon substituents, such as fluorenyl etc. “Arylene” respectively “heteroarylene”, refers to groups to which two further moieties are attached. In the present specification the term “aryl group” or “arylene group” may refer to a group comprising at least one hydrocarbon aromatic moiety, and all the elements of the hydrocarbon aromatic moiety may have p-orbitals which form conjugation, for example a phenyl group, a naphtyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, a fluorenyl group and the like. The aryl or arylene group may include a monocyclic or fused ring polycyclic (i.e., rings sharing adjacent pairs of carbon atoms) functional group.

The term “condensed aryl(ene) group” refers to an aryl group comprising at least two aromatic rings which are fused to each other by sharing two carbon atoms with each other. In this regard, it may be provided that the condensed aryl group (or the condensed arylene group) comprises more than two fused rings wherein each of the rings is fused with at least one other aryl ring of the condensed aryl(ene) by sharing with this one (or more) further ring(s) two carbon atoms. Non-limiting examples of such condensed aryl groups are fluoranthenyl, chrysenyl, pyrenyl etc.

The term “alkenyl” as used herein refers to a group —CR¹═CR²R³ comprising a carbon-carbon double bond.

The term “perhalogenated” as used herein refers to a hydrocarbyl group wherein all of the hydrogen atoms of the hydrocarbyl group are replaced by halogen (F, Cl, Br, I) atoms.

The term “alkoxy” as used herein refers to a structural fragment of the Formula —OR with R being hydrocarbyl, preferably alkyl or cycloalkyl.

The term “heteroaryl” as used herein refers to aromatic or aryl groups in which at least one carbon atom is substituted with a heteroatom, preferably selected from N, O, S, B or Si.

The subscripted number n in C_(n)-heteroaryl merely refers to the number of carbon atoms excluding the number of heteroatoms. In this context, it is clear that a C₃ heteroarylene group is an aromatic compound comprising three carbon atoms, such as pyrazol, imidazole, oxazole, thiazole and the like.

The term “heteroaryl” may refer to aromatic heterocycles with at least one heteroatom, and all the elements of the hydrocarbon heteroaromatic moiety may have p-orbitals which form conjugation. The heteroatom may be selected from N, O, S, B, Si, P, Se, preferably from N, O and S. A heteroarylene ring may comprise at least 1 to 3 heteroatoms. Preferably a heteroarylene ring may comprise at least 1 to 3 heteroatoms individually selected from N, S and/or O.

The term “heteroaryl” as used herewith shall encompass pyridine, quinoline, benzoquinoline, quinazoline, benzoquinazoline, pyrimidine, pyrazine, triazine, benzimidazole, benzothiazole, benzo[4,5]thieno[3,2-d]pyrimidine, carbazole, xanthene, phenoxazine, benzoacridine, dibenzoacridine, dibenzofurane, dibenzothiophene, phenanthroline and the like.

The term “fluorinated” as used herein refers to a hydrocarbon group in which at least one of the hydrogen atoms comprised in the hydrocarbon group is substituted by a fluorine atom. Fluorinated groups in which all of the hydrogen atoms thereof are substituted by fluorine atoms are referred to as perfluorinated groups and are particularly addressed by the term “fluorinated”.

In terms of the invention, a group is “substituted with” another group if one of the hydrogen atoms comprised in this group is replaced by another group, wherein the other group is the substituent.

In terms of the invention, the expression “between” with respect to one layer being between two other layers does not exclude the presence of further layers which may be arranged between the one layer and one of the two other layers. In terms of the invention, the expression “in direct contact” with respect to two layers being in direct contact with each other means that no further layer is arranged between those two layers. One layer deposited on the top of another layer is deemed to be in direct contact with this layer.

With respect to the inventive organic semiconductive layer as well as with respect to the inventive compound, the compounds mentioned in the experimental part are most preferred.

The inventive organic electronic device may be an organic electroluminescent device (OLED) an organic photovoltaic device (OPV), a lighting device, or an organic field-effect transistor (OFET). A lighting device may be any of the devices used for illumination, irradiation, signaling, or projection. They are correspondingly classified as illuminating, irradiating, signaling, and projecting devices. Alighting device usually consists of a source of optical radiation, a device that transmits the radiant flux into space in the desired direction, and a housing that joins the parts into a single device and protects the radiation source and light-transmitting system against damage and the effects of the surroundings.

According to another aspect, the organic electroluminescent device according to the present invention may comprise more than one emission layer, preferably two or three emission layers. An OLED comprising more than one emission layer is also described as a tandem OLED or stacked OLED.

The organic electroluminescent device (OLED) may be a bottom- or top-emission device.

Another aspect is directed to a device comprising at least one organic electroluminescent device (OLED).

A device comprising organic light-emitting diodes is for example a display or a lighting panel.

In the present invention, the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

In the context of the present specification the term “different” or “differs” in connection with the matrix material means that the matrix material differs in their structural Formula.

The terms “OLED” and “organic light-emitting diode” are simultaneously used and have the same meaning. The term “organic electroluminescent device” as used herein may comprise both organic light emitting diodes as well as organic light emitting transistors (OLETs).

As used herein, “weight percent”, “wt. %”, “percent by weight”, “% by weight”, and variations thereof refer to a composition, component, substance or agent as the weight of that component, substance or agent of the respective electron transport layer divided by the total weight of the respective electron transport layer thereof and multiplied by 100. It is under-stood that the total weight percent amount of all components, substances and agents of the respective electron transport layer and electron injection layer are selected such that it does not exceed too wt.-%.

As used herein, “volume percent”, “vol.-%”, “percent by volume”, “% by volume”, and variations thereof refer to a composition, component, substance or agent as the volume of that component, substance or agent of the respective electron transport layer divided by the total volume of the respective electron transport layer thereof and multiplied by 100. It is understood that the total volume percent amount of all components, substances and agents of the cathode layer are selected such that it does not exceed too vol.-%.

All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. As used herein, the term “about” refers to variation in the numerical quantity that can occur. Whether or not modified by the term “about” the claims include equivalents to the quantities.

It should be noted that, as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise.

The term “free of”, “does not contain”, “does not comprise” does not exclude impurities.

Impurities have no technical effect with respect to the object achieved by the present invention.

In the context of the present specification the term “essentially non-emissive” or “non-emissive” means that the contribution of the compound or layer to the visible emission spectrum from the device is less than 10%, preferably less than 5% relative to the visible emission spectrum. The visible emission spectrum is an emission spectrum with a wavelength of about ≥380 nm to about ≤780 nm.

Preferably, the organic semiconducting layer comprising the compound of Formula (I) is essentially non-emissive or non-emitting.

The operating voltage, also named U, is measured in Volt (V) at 10 milliAmpere per square centimeter (mA/cm2).

The candela per Ampere efficiency, also named cd/A efficiency is measured in candela per ampere at 10 milliAmpere per square centimeter (mA/cm2).

The external quantum efficiency, also named EQE, is measured in percent (%).

The color space is described by coordinates CIE-x and CIE-y (International Commission on Illumination 1931). For blue emission the CIE-y is of particular importance. A smaller CIE-y denotes a deeper blue color.

The highest occupied molecular orbital, also named HOMO, and lowest unoccupied molecular orbital, also named LUMO, are measured in electron volt (eV).

The term “OLED”, “organic light emitting diode”, “organic light emitting device”, “organic optoelectronic device” and “organic light-emitting diode” are simultaneously used and have the same meaning.

The term “life-span” and “lifetime” are simultaneously used and have the same meaning.

The anode electrode and cathode electrode may be described as anode electrode/cathode electrode or anode electrode/cathode electrode or anode electrode layer/cathode electrode layer.

Room temperature, also named ambient temperature, is 23° C.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

FIG. 2 is a schematic sectional view of an OLED, according to an exemplary embodiment of the present invention.

FIG. 3 is a schematic sectional view of a tandem OLED comprising a charge generation layer, according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present invention, by referring to the figures.

Herein, when a first element is referred to as being formed or disposed “on” or “onto” a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed there between. When a first element is referred to as being formed or disposed “directly on” or “directly onto” a second element, no other elements are disposed there between.

FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED) 100, according to an exemplary embodiment of the present invention. The OLED 100 includes a substrate 110, an anode 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, an electron transport layer (ETL) 160. The electron transport layer (ETL) 160 is formed on the EML 150. Onto the electron transport layer (ETL) 160, an electron injection layer (EIL) 180 is disposed. The cathode 190 is disposed directly onto the electron injection layer (EIL) 180.

Instead of a single electron transport layer 160, optionally an electron transport layer stack (ETL) can be used.

FIG. 2 is a schematic sectional view of an OLED 100, according to another exemplary embodiment of the present invention. FIG. 2 differs from FIG. 1 in that the OLED 100 of FIG. 2 comprises an electron blocking layer (EBL) 145 and a hole blocking layer (HBL) 155.

Referring to FIG. 2, the OLED 100 includes a substrate 110, an anode 120, a hole injection layer (IL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, an emission layer (EML) 150, a hole blocking layer (HBL) 155, an electron transport layer (ETL) 160, an electron injection layer (EIL) 180 and a cathode electrode 190.

Preferably, the organic semiconducting layer comprising a compound of Formula (I) may be an HBL.

FIG. 3 is a schematic sectional view of a tandem OLED 200, according to another exemplary embodiment of the present invention. FIG. 3 differs from FIG. 2 in that the OLED 100 of FIG. 3 further comprises a charge generation layer (CGL) and a second emission layer (151).

Referring to FIG. 3, the OLED 200 includes a substrate no, an anode 120, a first hole injection layer (HIL) 130, a first hole transport layer (HTL) 140, a first electron blocking layer (EBL) 145, a first emission layer (EML) 150, a first hole blocking layer (HBL) 155, a first electron transport layer (ETL) 160, an n-type charge generation layer (n-type CGL) 185, a hole generating layer (p-type charge generation layer; p-type GCL) 135, a second hole transport layer (HTL) 141, a second electron blocking layer (EBL) 146, a second emission layer (EML) 151, a second hole blocking layer (EBL) 156, a second electron transport layer (ETL) 161, a second electron injection layer (EIL) 181 and a cathode 190.

Preferably, the organic semiconducting layer comprising a compound of Formula (I) may be the first ETL, n-type CGL and/or second ETL.

While not shown in FIG. 1, FIG. 2 and FIG. 3, a sealing layer may further be formed on the cathode electrodes 190, in order to seal the OLEDs 100 and 200. In addition, various other modifications may be applied thereto.

Hereinafter, one or more exemplary embodiments of the present invention will be described in detail with, reference to the following examples. However, these examples are not intended to limit the purpose and scope of the one or more exemplary embodiments of the present invention.

Experimental Data Melting Point

The melting point (mp) is determined as peak temperatures from the DSC curves of the above TGA-DSC measurement or from separate DSC measurements (Mettler Toledo DSC822e, heating of samples from room temperature to completeness of melting with heating rate 10 K/min under a stream of pure nitrogen. Sample amounts of 4 to 6 mg are placed in a 40 μL Mettler Toledo aluminum pan with lid, a <1 mm hole is pierced into the lid).

Glass Transition Temperature

The glass transition temperature (Tg) is measured under nitrogen and using a heating rate of 10 K per min in a Mettler Toledo DSC 822e differential scanning calorimeter as described in DIN EN ISO 11357, published in March 2010.

Rate Onset Temperature

The rate onset temperature (T_(RO)) is determined by loading 100 mg compound into a VTE source. As VTE source a point source for organic materials may be used as supplied by Kurt J. Lesker Company (www.lesker.com) or CreaPhys GmbH (http://www.creaphys.com). The VTE source is heated at a constant rate of 15 K/mmi at a pressure of less than 10⁻⁵ mbar and the temperature inside the source measured with a thermocouple. Evaporation of the compound is detected with a QCM detector which detects deposition of the compound on the quartz crystal of the detector. The deposition rate on the quartz crystal is measured in Ångstrom per second. To determine the rate onset temperature, the deposition rate is plotted against the VTE source temperature. The rate onset is the temperature at which noticeable deposition on the QCM detector occurs. For accurate results, the VTE source is heated and cooled three time and only results from the second and third run are used to determine the rate onset temperature.

To achieve good control over the evaporation rate of an organic compound, the rate onset temperature may be in the range of 200 to 255° C. If the rate onset temperature is below 200° C. the evaporation may be too rapid and therefore difficult to control. If the rate onset temperature is above 255° C. the evaporation rate may be too low which may result in low tact time and decomposition of the organic compound in VTE source may occur due to prolonged exposure to elevated temperatures.

The rate onset temperature is an indirect measure of the volatility of a compound. The higher the rate onset temperature the lower is the volatility of a compound.

Reduction Potential

The reduction potential is determined by cyclic voltammetry with potentiostatic device Metrohm PGSTAT30 and software Metrohm Autolab GPES at room temperature. The redox potentials given at particular compounds were measured in an argon de-aerated, dry 0.1M THF solution of the tested substance, under argon atmosphere, with 0.1M tetrabutylammonium hexafluorophosphate supporting electrolyte, between platinum working electrodes and with an Ag/AgCl pseudo-standard electrode (Metrohm Silver rod electrode), consisting of a silver wire covered by silver chloride and immersed directly in the measured solution, with the scan rate 100 mV/s. The first run was done in the broadest range of the potential set on the working electrodes, and the range was then adjusted within subsequent runs appropriately. The final three runs were done with the addition of ferrocene (in 0.1M concentration) as the standard. The average of potentials corresponding to cathodic and anodic peak of the studied compound, after subtraction of the average of cathodic and anodic potentials observed for the standard Fc⁺/Fc redox couple, afforded finally the values reported above. All studied compounds as well as the reported comparative compounds showed well-defined reversible electrochemical behaviour.

Dipole Moment

The dipole moment |{right arrow over (μ)}| of a molecule containing N atoms is given by:

$\overset{\rightharpoonup}{\mu} = {\sum\limits_{i}^{N}\;{q_{i}{\overset{\rightharpoonup}{r}}_{i}}}$ ${\overset{\rightharpoonup}{\mu}} = \sqrt{\mu_{x}^{2} + \mu_{y}^{2} + \mu_{z}^{2}}$

where q_(i) and {right arrow over (r_(i))} are the partial charge and position of atom i in the molecule.

The dipole moment is determined by a semi-empirical molecular orbital method.

The geometries of the molecular structures are optimized using the hybrid functional B3LYP with the 6-31G* basis set in the gas phase as implemented in the program package TURBOMOLE V6.5 (TURBOMOLE GmbH, Litzenhardtstrasse 19, 76135 Karlsruhe, Germany). If more than one conformation is viable, the conformation with the lowest total energy is selected to determine the bond lengths of the molecules.

Calculated HOMO and LUMO

The HOMO and LUMO are calculated with the program package TURBOMOLE V6.5 (TURBOMOLE GmbH, Litzenhardtstrasse 19, 76135 Karlsruhe, Germany). The optimized geometries and the HOMO and LUMO energy levels of the molecular structures are determined by applying the hybrid functional B3LYP with a 6-31G* basis set in the gas phase. If more than one conformation is viable, the conformation with the lowest total energy is selected.

General synthetic procedure for the preparation of compounds of formula (I):

Intermediate Ring Formation Step:

Synthesis of 3-bromobenzo[4,5]imidazo[1,2-a]quinoline

Under an inert nitrogen atmosphere, 2-methyl-1H-benzo[d]imidazole (10.0 g, 75.7 mmol, 1.0 eq) and potassium carbonate (31.37 g, 226.9 mmol, 3.0 eq) were placed in a 1 L 2-necked flask. Diethyl sulfoxide (DMSO, 375 mL) was added in a single portion in a counterflow of nitrogen, followed by 5-Bromo-2-fluorobenzaldehyde (18.43 g, 90.8 mmol, 1.2 eq). The mixture was heated to +12° C. and stirred over 3 hours, maintaining the inert conditions. After cooling down, the mixture was added to water (1.200 mL) and extracted with ethyl acetate (1×300 mL, 2×100 mL). As much precipitate formed in the combined organic layers, the solid was separated via filtration, washed with small amounts of n-hexane and methanol and dried in a vacuum oven overnight to give 7.5 g (33% yield) with a purity of GC 98%. Two further fractions (3.0 g, 13% yield, GC 96.2% and 0.8 g, 3.5% yield, GC 99.0%) were obtained from mother liquor work-up.

Synthesis of 3-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)benzo[4,5]imidazo[1,2-a]quinoline

Under an inert nitrogen atmosphere, 3-bromobenzo[4,5]imidazo[1,2-a]quinoline (5.4 g, 18.2 mmol, 1.0 eq), 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine (7.91 g, 18.7 mmol, 1.0 eq), Tetrakis(triphenylphosphin)-palladium(0) (0.42 g, 0.36 mmol, 2 mol %) and potassium carbonate (5.02 g, 36.3 mmol, 2.0 eq) were placed in a 500 mL reaction vessel. Afterwards, 1,4-dioxane (273 mL) and degassed water (18 mL) were added. The yellow suspension was heated to +9° C. and stirred overnight, maintaining the inert atmosphere. Reaction progress was monitored using TLC (silica, dichloromethane/n-hexane 3:2 vol/vol). The mixture was cooled to room temperature, filtered and the filter residue was successively washed with water (2×00 mL) and methanol (2×100 mL) and dried in a vacuum oven at +50° C. overnight. The grey crude material was dissolved in hot chlorobenzene (2.000 mL), filtered (hot) through a pressed pad of silica and the pad was rinsed with further chlorobenzene (400 mL) to remove side-products. Afterwards, the product was eluted using chlorobenzene/ethyl acetate mixtures (2×500 mL of a 2:1 (vol/vol) and 1×500 mL of a 1:1 (vol/vol) mixture). The product precipitated from the filtrate overnight and was isolated via filtration, washed with dichloromethane (2×20 mL) and dried in a vacuum oven at +120° C. for 1 hour. The product was obtained as 2.79 g (29% yield) of a pale yellow solid with an HPLC purity of 99.91%. Final purification was done by gradient sublimation with a sublimation yield of 82%.

Synthesis of 7-(3-(benzo[4,5]imidazo[1,2-a]quinolin-3-yl)phenyl)dibenzo[c,h]acridine

Under an inert nitrogen atmosphere, 3-bromobenzo[4,5]imidazo[1,2-a]quinoline (5.0 g, 16.8 mmol, 1.0 eq), 7-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)dibenzo[c,h]acridine (8.1 g, 16.8 mmol, 1.0 eq), Tetrakis(triphenylphosphin)palladium(0) (0.38 g, 0.37 mmol, 2 mol %) and potassium carbonate (4.65 g, 33.6 mmol, 2.0 eq) were placed in a 500 mL reaction vessel. Afterwards, 1,4-dioxane (67 mL) and degassed water (17 mL) were added. The yellow suspension was heated to +90° C. and stirred overnight, maintaining the inert atmosphere. Reaction progress was monitored using TLC (silica, dichloromethane/n-hexane 3:2 vol/vol). The mixture was filtered and the filter residue was successively washed with water (300 mL); methanol and n-hexane. The grey crude material was dissolved in dichloromethane (2.000 mL), filtered through a pressed pad of silica and the pad was rinsed with a mixture of ethyl acetate/dichloromethane 1:3 (vol/vol, 1.600 mL). Filtrate fractions were collected and first eluting side-compounds were removed. The product fractions were combined and concentrated to dryness to give 4.4 g material. Recrystallization from toluene (700 mL) followed by drying in vacuo at +120° C. for 1 hour gave 3.65 g (38% yield) of a pale yellow powder with an HPLC purity of 100%. Final purification was done by gradient sublimation with a sublimation yield of 73%.

Synthesis of 3-(10-([1,1′-biphenyl]-4-yl)anthracen-9-yl)benzo[4,5]imidazo[1,2-a]quinolone

Under an inert nitrogen atmosphere, 3-bromobenzo[4,5]imidazo[1,2-a]quinolone (7.94 g, 26.7 mmol, 1.0 eq), (10-([1,1′-biphenyl]-4-yl)anthracen-9-yl)boronic acid (10.0 g, 26.7 mmol, 1.0 eq), Tetrakis(triphenylphosphin)-palladium(10) (0.62 g, 0.53 mmol, 2 mol %) and potassium carbonate (7.38 g, 53.4 mmol, 2.0 eq) were placed in a 500 mL reaction vessel. Afterwards, tetrahydrofuran (THF, 80 mL) and degassed water (20 mL) were added. The beige suspension w as heated to +75° C. and stirred overnight, maintaining the inert atmosphere. Reaction progress was monitored using TLC (silica, dichloromethane with 4% methanol) and HPLC. As there was still a significant amount of not-reacted starting bromide, [1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) was added (0.5 mol % after 22 hours and 2.0 mol % after 45 hours), followed by toluene (75 mL) and ethanol (25 mL) and the temperature was raised to +105° C. After 79 hours total reaction time, the mixture was cooled down to +5° C., filtered and the filter residue was washed with THF and water (1.300 mL). The crude material was placed in a Soxhlet sleeve and extracted with chlorobenzene overnight. The extract was concentrated, filtered and the filter residue was treated with hot chlorobenzene and extracted in the Soxhlet, again. The product from the second extract was obtained as 2.58 (17% yield) of a beige solid with an HPLC purity of 99.53%. Final purification was done by gradient sublimation with a sublimation yield of 55%.

For the top emission OLED devices of example-1 and of the comparative example a substrate with dimensions of 150 mm×150 mm×0.7 mm was ultrasonically cleaned with a 2% aquatic solution of Deconex FPD 211 for 7 minutes and then with pure water for 5 minutes, and dried for 15 minutes in a spin rinse dryer. Subsequently, Ag was deposited as anode at a pressure of 10-5 to 10-7 mbar.

Then, HT-1 and D-1 were vacuum co-deposited on the anode to form a HIL. Then, HT-1 was vacuum deposited on the HIL, to form an HTL. Then, HT-2 was vacuum deposited on the HTL to form an electron blocking layer (EBL).

Afterwards the emission layer was formed on the EBL by co-deposition of HOST-1 and EMITTER-1.

Then, the ET-1 was vacuum deposited onto the emission layer to form the hole blocking layer (HBL). Then, the electron transport layer was formed on the hole blocking layer by co-depositing a compound of formula (I) and LiQ.

Then, the electron injection layer is formed on the electron transporting layer by deposing Yb.

Ag:Mg is then evaporated at a rate of 0.01 to 1 Å/s at 10-7 mbar to form a cathode.

A cap layer of HT-1 is formed on the cathode.

The details of the layer stack in the top emission OLED devices are given below. A slash “/” separates individual layers. Layer thicknesses are given in squared brackets [ . . . ], mixing ratios in wt % given in round brackets ( . . . ):

Layer Stack Details:

Ag [100 nm]/HT-1:D-1 (92:8) [10 nm]/HT-1 [118 nm]/HT-2 [5 nm]/H09:BD200 (97:3) [20 nm]/ET-1 [5 nm]/Compound of formula (I): LiQ (1:1) [31 nm]/Yb [2 nm]/Ag [13 nm]/HT-1 [70 nm]

Technical Effect of the Invention

The OLED devices according to the invention show improved EQE efficiency and lower voltage when using the compounds of formula (I) in an electron transport layer instead of the prior art compound.

List of Compounds Used

IUPAC name Reference HT-1 N-([1,1′-biphenyl]-4-yl)-9,9-dimethyl- US2016322581 N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)- 9H-fluoren-2-amine [CAS 1242056-42-3] HT-2 N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)- JP2014096418 [1,1′:4′,1″-terphenyl]-4-amine [CAS 1198399-61-9] D-1 4,4′,4″-((1E,1′E,1″E)-cyclopropane- US2008265216 1,2,3-triylidenetris(cyanomethanyl- ylidene))tris(2,3,5,6-tetrafluorobenzonitrile) [CAS 1224447-88-4] HOST-1 Ho9 (Fluorescent-blue host material) Commercially available from Sun Fine Chemicals, Inc, S. Korea EMIT- BD200 (Fluorescent-blue host material) Commercially TER-1 available from Sun Fine Chemicals, Inc, S. Korea ET-1 2,4-diphenyl-6-(4′,5′,6′-triphenyl- WO2016171358 [1,1′:2′,1″:3″,1′″:3′″,1″″-quinquephenyl]- 3″″-yl)-1,3,5-triazine [CAS 2032364-64-8] Com- 7-(4′-(1-phenyl-1H-benzo[d]imidazol-2-yl)- WO2013079676 parative-1 [1,1′-biphenyl]-4-yl)dibenzo[c,h]acridine LiQ 8-Hydroxyquinolinolato-lithium WO2013079217 [CAS 850918-68-2]

TABLE 1 Properties of compounds Inv-1 to Inv-3 of formula (I) and of compound Comparative-1 Dipole moment mp Tg T_(RO) Molecular Structure [Debye] [° C.] [° C.] [° C.] Comparative-1

3,78 372 — 303 Inv-1

— 276 120 243 Inv-2

3,12 299 161 286 Inv-3

3,78 430 — 299

TABLE 2 Performance of an organic electroluminescent device comprising the compounds of formula (1) as a matrix material in the electron transport layer Operating voltage at EQE at OLED device Matrix n- 10 mA/ 10 mA/ examples material additive cm² (V) cm² Comparative Com- LiQ 3.88 7.05 example parative-1 Example-1 Inv-2 LiQ 3.57 7.69

The features disclosed in the foregoing description and in the dependent claims may, both separately and in any combination thereof, be material for realizing the aspects of the disclosure made in the independent claims, in diverse forms thereof. 

1. Compound of formula (I)

wherein R¹ and R² are independently selected from the group consisting of substituted or unsubstituted C₆ to C₄₈ aryl and substituted or unsubstituted C₂ to C₄₂ heteroaryl; the substituents of R¹ and R², if present, are selected from the group consisting of deuterium, fluorine, RF, C₁ to C₂₀ linear alkyl, C₃ to C₂₀ branched alkyl, C₁ to C₁₂ linear fluorinated alkyl, CN, RCN, C₆ to C₂₀ aryl, C₂ to C₂₀ heteroaryl, P(═O)R′R″, wherein each R, R′ and R″ is independently selected from the group consisting of C₁ to C₂₀ linear alkyl, C₁ to C₂₀ alkoxy, C₁ to C₂₀ thioalkyl, C₃ to C₂₀ branched alkyl, C₃ to C₂₀ cyclic alkyl, C₃ to C₂₀ branched alkoxy, C₃ to C₂₀ cyclic alkoxy, C₃ to C₂₀ branched thioalkyl, C₃ to C₂₀ cyclic thioalkyl, C₆ to C₂₀ aryl and C₂ to C₂₀ heteroaryl; n and m are independently selected from 0, 1, 2 and n+m≥1; n and m are independently selected from 0, 1, 2 and n+m≥1; wherein at least one of R¹ and R² is connected to the ring Y, respectively the ring Z, by a spacer unit, wherein the spacer unit is independently selected from substituted or unsubstituted C₆ to C₁₈ arylene or substituted or unsubstituted C₂ to C₂₀ heteroarylene; wherein in case that the spacer unit is substituted the one or more substituent(s) are independently selected from the group consisting of deuterium C₆ to C₁₄ aryl, C₂ to C₂₀ heteroaryl, CN-substituted C₆ to C₁₄ aryl, CN, P(═O)R′R″, wherein R′ and R″ may be the same or different and are independently selected from C₁ to C₁₀ alkyl or C₆ to C₁₂ aryl; provided that if the spacer unit is phenylene or phenyl-substituted phenylene the group R¹, respectively R², connected via this spacer unit to the ring Y, respectively Z, is not phenyl; provided that if the spacer unit is C₂ to C₂₀ heteroaryl, then at least one of a substituent on the spacer unit and the group R¹, respectively R², connected to the spacer unit is a heteroaryl.
 2. Compound according to claim 1, wherein the total number of aromatic rings in the molecule is from 6 to
 15. 3. Compound according to claim 1, wherein the spacer unit is selected from C₆ to C₁₄ aryl, O-containing C₃ to C₁₂ heteroaryl, or N-containing C₃ to C₁₂ heteroaryl.
 4. Compound according to claim 1, wherein the spacer unit is selected from phenylene, biphenylene, naphthylene, anthracenylene, pyridinylene, diazinylene, dibenzofuranylene and triazinylene, wherein the respective group may be substituted or unsubstituted.
 5. Compound according to claim 1, wherein the spacer unit is selected from substituted or unsubstituted C₆ to C₁₄ arylene.
 6. Compound according to claim 1, wherein the groups R¹ and R² are independently selected from C₆ to C₁₈ aryl, O-containing C₃ to C₁₇ heteroaryl or N-containing C₃ to C₁₇ heteroaryl.
 7. Compound according to claim 1, wherein R¹ and R² are independently selected from the group consisting of phenyl, biphenyl, naphthyl, anthracenyl, dibenzofuranyl, pyridyl, diazinyl, triazinyl, phenanthrolinyl, carbazolyl, benzoacridinyl, quinazolinyl, and fluoranthenyl, wherein the respective group may be substituted or unsubstituted.
 8. Compound according to claim 1, wherein the one or more substituent(s) if present on the spacer unit and/or the group R¹ and/or the group R² are independently selected from C₆ to C₁₄ aryl, O-containing C₄ to C₁₂ heteroaryl, N-containing C₄ to C₁₂ heteroaryl, cyanophenyl, CN or P(═O)R₂ with R being methyl or phenyl.
 9. Compound according to claim 1, wherein the one or more substituent(s) if present on the spacer unit and/or the group R¹ and/or the group R² are independently selected from the group consisting of phenyl, biphenyl, naphthyl, dibenzofuranyl, cyanophenyl, diphenylphosphinoxide, dimethylphosphinoxide, CN, 9,9-dimethylfluorenyl, carbazolyl and pyridinyl.
 10. Organic semiconducting layer comprising the compound of Formula (I) according to claim
 1. 11. Organic semiconducting layer according to claim 10, wherein the organic semiconducting layer comprises an n-type additive wherein the n-type additive is selected from a metal, a metal salt or a metal complex.
 12. Organic semiconducting layer according to claim 10, wherein the organic semiconducting layer further comprises at least one second matrix compound.
 13. Organic electronic device comprising the organic semiconducting layer according to any of the claim
 10. 14. Display device comprising the organic electronic device according to claim
 13. 15. Lighting device comprising the organic electronic device according to claim
 13. 16. Compound according to claim 1, wherein n+m is from 1 to
 3. 